1. Field of the Invention
The invention relates to a device for unloading an open-top tray filled with flat articles, e.g. mailpieces, that are placed in a stack on the bottom of the tray, the device including a pivot member suitable for taking hold of the tray and for tilting its opening downwards.
2. Discussion of the Background Art
In general, during a mail sorting process, the mailpieces are transported in stacks inside trays by conveyors, and they are unloaded by an operator at a Tray Unloading Device (TUD). For example, the trays are brought from the sorting outlets of a sorting machine or from the outside towards the tray unloading device where the mailpieces are unloaded and then transferred to a feed magazine where the mailpieces are unstacked so as then to be transported towards other steps of the sorting process.
Document EP 1 829 804 discloses an unloading device for automatically unloading articles, e.g. mailpieces, contained in a tray conveyed by a conveyor. That unloading device comprises a clamping and pivoting device 50 that firstly holds the tray firmly between a lid 21 and a base 48, and that secondly causes the tray to pivot with the lid about a horizontal axis via articulated arms 22, 45, 47, so as to cause the mailpieces to slide out of the tray via an opening 53 formed in the lid 21 and so as to direct them onto a guide plate 23. However, while the tray is pivoting, the operator keeps a hand on the mailpieces so as to prevent them from slipping on one another and from falling into the tray too early, and then the operator must help the mailpieces to slide out of the pivoted tray.
Patent Document U.S. Pat. No. 7,195,236 also discloses a system for unloading articles contained in a tray and for conveying them on a conveyor 20 to a feed magazine. The mailpieces F are initially placed in a stack on edge in a tray 160 that has a retractable or removable front wall 160FR and that is transported by a conveyor 110 to an elevator 200 that lowers the mailpieces to the unloading system. That unloading system includes a device for raising the front wall 160FR of the tray and a paddle 30 that is mounted to move vertically and horizontally and that is designed to be inserted into the tray between the mailpieces and a back wall 160B of the tray, and then to push the mailpieces out of the tray, so that the mailpieces are transported directly on another conveyor 20 towards the feed unit. The paddle is comb-shaped and its teeth 30T are complementary to tines 160T on the back wall 160B of the tray so as to facilitate inserting the paddle between the mailpieces and the back wall of the tray. A plurality of paddles 30-1, 30-2, 30-3 disposed in front of the first paddle serve to straighten up the mailpieces on the conveyor. However, in that system, it is an operator who initially loads the mailpieces in a stack on edge into the tray.
The use of such unloading systems raises certain problems. For example, the trays must be transferred manually from the unloading point of the unloading system, and that is an arduous and tiring task for the operator in view of the weights of the trays and of the mailpieces, and of the distance to go along the conveyor for unloading each tray. In addition, the rate of throughput of the machine is slowed down because the operator cannot feed the feed magazine as quickly as would be necessary to keep up with the speed of the feed magazine.
Document US 2007/0201968 also discloses a system for unloading mailpieces at the end of sorting from a standard tray to a shuttle while putting them in a stack, and then for unloading the stack of mailpieces from the shuttle to a special tray for a feed magazine. The standard tray 9 is loaded manually or automatically onto an unloading device having a pivot frame 22 provided with a closure plate for closing and blocking the tray 9. The pivot frame pivots about a horizontal axis so as to cause the opening of the tray to face downwards, and a shuttle 8 is brought by a conveyor under the pivot frame, so as to receive the mailpieces 10 once the closure plate has been removed. The shuttles have V-shaped bottoms so as to jog and align the mailpieces. Then the shuttles are brought by a conveyor to a pivot device 52 so as to empty the mailpieces from the shuttle onto a surface 66 by means of a comb-shaped paddle 74 having its teeth complementary to ribs 86 on a wall of each of the shuttles. A plurality of pallets 73, 74 and 78, 79 serve to push the mailpieces towards the special tray 12 from which a removable or retractable wall is removed in order to enable the mailpieces to be loaded.